Glomerular filtration rate is the amount of filtrate formed in which anatomical structures per minute?

• A. Amount of filtrate formed in all the renal corpuscles of both kidneys each minute
• B. Total urine produced per day
• C. Blood flow to the kidneys per minute
• D. Rate of urine concentration in the collecting ducts

Answer: (A)

Glomerular filtration rate is the volume of filtrate produced per minute by all the glomeruli in the kidneys. This filtrate forms when plasma passes through the glomerular membrane into Bowman's capsule, and the rate is the sum across every functioning renal corpuscle in both kidneys. In a healthy adult, this rate is about 125 mL per minute (roughly 180 liters per day). Most of this filtrate is subsequently reabsorbed along the tubules, so urine output is a small fraction of the filtrate.

The other options describe different renal processes: total urine per day is the final excreted product, not the rate of filtrate formation; blood flow to the kidneys per minute refers to perfusion, not filtration; and the rate of urine concentration in the collecting ducts reflects water reabsorption and osmolar handling, not how much filtrate is formed.